MACHINE STRENGTH GRADING - LUMBER AND TIMBER
PRECIGRADER

Machine strength (stress) grading with Precigrader is based on an accurate measurement of the wood E-modulus (MOE) and wood density of each passing piece. The efficient strength grading is done for over 180 lpm. In many case, the wood E-modulus (MOE) is the governing parameter for a certain strength class and raw-material. This fact and the strong correlation to wood strength makes Precigrader an optimal solution for machine strength grading of lumber or timber. Machine strength grading can be done in accordance with various product standards and grading rules. Typical strength classes in Europe are C18, C24, TR26 (UK) and C30, and in North America the MSR-grades like 1650f and 2100f.

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Accurately measured wood E-modulus (MOE) and wood density

Precigrader utilizes the potential of the wood raw material in the absolute best way through an accurate strength sorting. The measured dynamic E-modulus (MOE) provides a best estimate of the static E-modulus and bending or tensile strength. An accurately measured wood density is given together with the strength grade and E-modulus as output to the receiving PLC.

Simple and cost-effective strength grading in transfer lines

Precigrader efficiently grades structural lumber/timber and glulam laminations, and is easily installed in a transfer line in sorting mills and planer mills. The required space is less than 1.5 meters (5 ft). The high capacity of over 180 lpm fulfills the demands of most lines.

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A safe and proven system – simple and reliable principle

The dynamic measurement technology is based on the long experience from Dynagrade which was first installed 20 years ago. The first Precigrader system was running in 2006. Since then, millions of boards have also passed this system type. A spring-loaded impact mechanism (a kind of hammer) in the main unit is activated by the cross-conveyed lumber/timber. Each stroke generates vibrations in the wood, and the generated sound is captured by robust high-tech microphones. At the same time, the length, size and wood density of the piece is measured (length and size alternatively imported from the PLC). The timber piece rests on special low-friction supports during the measurement itself, during the continuous operation.

Applicability

Precigrader is approved in accordance with the European standard EN 14081 for machine strength grading of structural timber (C-grades) and glulam laminations (T-grades according to EN 14080). Precigrader is also approved in Canada and in the USA for MSR grading. Precigrader is also approved for grading of glulam laminations according to the Japanese standard JAS. Grading of Australian MGP grades is also done today with Precigrader in Europe for lumber export to Australia. Precigrader can also be used for other quality control where the wood E-modulus (MOE) and wood density are in focus rather than the strength grading.

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Precigrader is based on the measurement of resonance frequencies, length, dimension and lumber weight. It is designed to be robust, simple-to-use and offers a wide spectrum of grading applications.

 

Main prerequisites:

  • Limber or timber size and length 1):

Thickness 19-110 mm, Width 60-300 mm, Length 1200-7200 mm

  • Sawn or planed surface
  • Dried or green lumber/timber, cut to angle at least in the sawmill
  • Required space: less than 1,5 meter (5 ft) of a transfer line with lugged chains
  • Strength grade, grading parameter and length output via RS232 and/or TCP/IP.

1) Length interval is max 4800 mm when measured with the optional length reader, i.e. a fixed interval from 1200-6000 mm up to 2400-7200 mm. No limitation in interval for imported length. Various standards and approvals may limit the size and length intervals.

Precigrader has been installed in many mills in Austria, the Baltics, Belgium, Finland, Germany, Norway, Russia, Sweden. Some references are:

 

Precigrader is based on the Dynagrade technology.

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Denmark, Norway & Sweden

Finland, Estonia, Latvia, Lithuania, Poland & Russia

Great Britain & Ireland

Canada & USA

Switzerland, Germany & Austria

France & Belgium

Japan